### Combination reaction.

When two or more substances combine (mixture or compounds) to form a single product, then the reaction is called as combination reaction.

Endothermic reactions:
The reactions in which heat is absorbed are called endothermic reactions. The reactants absorb heat for form products.

Oxidation reaction.

The chemical reaction in which reactants gain oxygen to form corresponding oxide. Also, A chemical reaction in which reactants lose hydrogen to form product is called oxidation.